Steroid hormones secreted by the gonads contribute to developmental, seasonal, and individual variations in mammalian social behaviors. Testicular androgens, for example, often influence the sexual and communication patterns of males both developmentally and in adulthood. The goal of the proposed research is to improve our understanding of the relationship between hormones and behavior by studying the mechanisms of androgen action on the brain. Various techniques, including direct application of hormones to the brain, lesioning of discrete brain regions, and steroid hormone autoradiography, will be used to identify brain regions that are sensitive to androgens and that control male sociosexual behaviors. Questions about the role of androgen metabolism in the stimulation of behavior will be addressed by identifying androgen metabolites present in brain regions that control social behaviors and by studying the behavioral effects of drugs that inhibit androgen metabolism. The possibility that androgens influence social behaviors by altering RNA and protein synthesis in the brain will be studied by using drugs that disrupt RNA synthesis and by using immunochemical techniques to assess hormone-induced changes in protein synthesis. Finally, the possibility that sex differences in behavioral sensitivity to hormones result from sex differences in the capacity of brain cell chromatin to bind hormones will be studied by analyzing the binding properties of chromatin from discrete brain regions and by comparing chromatin binding between groups of animals that differ in their sensitivity to steroids as a result of exposure to hormones during early development. This research will be performed using androgen-sensitive sexual and communication behaviors of rodents as model systems.